(a) Field of the Invention
The present invention relates to a chemically amplified resist, more in particular to the chemically amplified resist having excellent controllability with respect to dimensions and shapes and being responsive to the design rule of 0.15 xcexcm or less.
(b) Description of the Related Art
A higher integration and a finer design rule have been achieved in the field of LSI together with development miniaturization and higher performance of the semiconductor devices. This accelerates development of photolithographic technology for stably conducting the miniaturization processing of the semiconductor device having a line width of 0.18 xcexcm or less with a higher accuracy.
In the conventional exposure method using visible rays having a wavelength between 400 and 700 nm or near ultraviolet rays having a wavelength between 300 and 400 nm, fine processing for a pattern having a line width of 0.18 xcexcm or less can be hardly conducted. A method for using, as exposure light, far ultraviolet rays such as KrF excimer laser rays having a wavelength of 248 nm is researched as the photolithographic technology which may meet the design rule applied to the finer pattern and has a wider range of a focal depth. A chemically amplified resist is proposed as higher resolution resist applicable to such the short wavelength rays (radiation), and is researched for commercialization.
The chemically amplified resist contains, as a component, a radiation-sensitive acid generator which generates an acid upon exposure to light in addition to resin which is the main component thereof. Chemical reactions such as change of polarities and cleavage of a chemical bond progress in the resin of the resist film due to the catalysis of the acid, and the solubility into the developer in the exposing section is changed.
The chemically amplified resist forms patterns by utilizing the change of the solubility into the developer in the exposing section due to the elimination of a protection group by the acid catalysis.
A chemically amplified resist conventionally used contains hydroxystyrene resin represented by the general formula [1] and a radiation-sensitive acid generator dissolved in a solvent in a weight ratio of 16.0:0.80:83.20 in this turn, and 40% of hydroxyl groups of the hydroxystyrene resin are protected by ethoxyethyl groups.
For patterning an interconnect layer by using the conventional resist by means of the pattern transfer, exposure is conducted by using a stepper in which the KrF excimer laser rays having the wavelength of 248 nm is used as exposure light.
However, in the conventional resist, the unsatisfactorily controllability with respect to the dimensions and the shape does not reach to the level of commercialization which responds to the 0.15 xcexcm design rule.
The present inventor has confirmed this fact by the following experiment. An organic thin-film having a thickness of 0.10 xcexcm was deposited, as a reflection preventing film, on an interconnect layer made of polycrystalline silicon. The conventional chemically amplifying resist was applied thereon to form a resist layer having a thickness of 0.50 xcexcm. The exposure was conducted through a mask pattern by using the stepper employing the KrF excimer laser rays as the exposure light under the conditions that the number of apertures (NA) was 0.60 and a coherent factor ("sgr") was 0.75, thereby forming a pattern of isolated lines having a thickness of 0.15 xcexcm after the development.
The thus obtained resist pattern 11 as shown in FIG. 1 included an undesired rounded top shape, and the interface 12 between the resist layer and the reflection preventing layer 13 was not linear but intensely zigzagged as shown in FIG. 1. When the polycrystalline silicon layer 14 was etched by using the above pattern as the mask, the roughness of the side wall 15 of the polycrystalline silicon layer 14 was increased.
After the lapse of 3 hours"" standing upon the exposure, the pattern was developed. The pattern dimensions were not settled in the critical dimensions (CD) which were 0.15 xcexcmxc2x110%.
The rounded top provided the poor durability to the etching, and the unsatisfactory controllability with respect to the pattern dimensions and shapes.
The photolithography satisfying the 0.15 xcexcm rule cannot be conducted which is a standard rule for fabricating a future semiconductor device.
In view of the foregoing, an object of the present invention is to provide a chemically amplified resist having the excellent controllability with respect to dimensions and shapes and being responsive to the 0.15 xcexcm design rule.
Thus, the present invention provides a chemically amplified resist including hydroxystyrene resin protected by an ethoxyethyl group and acting as base resin, the hydroxystyrene resin having a molecular weight between 5000 and 20000 and represented by a general formula [1]; a radiation-sensitive acid generator; polystyrene acting as a filler and having a molecular weight between 150 and 20000; and a solvent for dissolving the base resin, the acid generator and the filler, wherein a content of the hydroxystyrene resin is between 10 and 20% in weight with respect to the entire chemically amplified resist, contents of the acid generator and the filler are between 1 and 15% in weight and between 0.5 and 6.0% in weight, respectively, with respect to the base resin, and a balance is the solvent. 
In accordance with the present invention, the chemically amplified resist having the excellent controllability with respect to dimensions and shapes can be obtained because a free volume of the chemically amplified resist is reduced by filling a free volume in the chemically amplified resist with the filler.
The above and other objects, features and advantages of the present invention will be more apparent from the following description.